- Virtio-msg - lists.linaro.org

by Bill Mills

All, I have updated the December wiki page with the notes from today. Any fixes are appreciated. https://linaro.atlassian.net/wiki/spaces/HVAC/pages/30510383105/2025-12+Upd… The page has a link and password to the recording and transcript if you want to see or hear the whole thing. Thanks, Bill -- Bill Mills Principal Technical Consultant, Linaro +1-240-643-0836 TZ: US Eastern Work Schedule: Tues/Wed/Thur

10 months

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[PATCH] dma-buf: add no-op stubs when CONFIG_DMA_SHARED_BUFFER is disabled

by Viresh Kumar

Move several dma-buf function declarations under CONFIG_DMA_SHARED_BUFFER and provide static inline no-op implementations for the disabled case to allow the callers to build when the feature is not compiled in. Signed-off-by: Viresh Kumar <viresh.kumar(a)linaro.org> --- include/linux/dma-buf.h | 116 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 116 insertions(+) diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index d58e329ac0e7..06e494d8f6b0 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -568,6 +568,7 @@ static inline bool dma_buf_is_dynamic(struct dma_buf *dmabuf) return !!dmabuf->ops->pin; } +#ifdef CONFIG_DMA_SHARED_BUFFER struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf, struct device *dev); struct dma_buf_attachment * @@ -609,4 +610,119 @@ int dma_buf_vmap_unlocked(struct dma_buf *dmabuf, struct iosys_map *map); void dma_buf_vunmap_unlocked(struct dma_buf *dmabuf, struct iosys_map *map); struct dma_buf *dma_buf_iter_begin(void); struct dma_buf *dma_buf_iter_next(struct dma_buf *dmbuf); + +#else +static inline struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf, + struct device *dev) +{ + return NULL; +} + +static inline struct dma_buf_attachment * +dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev, + const struct dma_buf_attach_ops *importer_ops, + void *importer_priv) +{ + return NULL; +} + +static inline void dma_buf_detach(struct dma_buf *dmabuf, + struct dma_buf_attachment *attach) { } + +static inline int dma_buf_pin(struct dma_buf_attachment *attach) +{ + return -EOPNOTSUPP; +} + +static inline void dma_buf_unpin(struct dma_buf_attachment *attach) { } + +static inline struct dma_buf * +dma_buf_export(const struct dma_buf_export_info *exp_info) +{ + return NULL; +} + + +static inline int dma_buf_fd(struct dma_buf *dmabuf, int flags) +{ + return -EOPNOTSUPP; +} + + +static inline struct dma_buf *dma_buf_get(int fd) +{ + return NULL; +} + +static inline void dma_buf_put(struct dma_buf *dmabuf) { } + +static inline struct sg_table * +dma_buf_map_attachment(struct dma_buf_attachment *, enum dma_data_direction) +{ + return NULL; +} + +static inline void dma_buf_unmap_attachment(struct dma_buf_attachment *, + struct sg_table *, + enum dma_data_direction) { } + +static inline void dma_buf_move_notify(struct dma_buf *dma_buf) { } + +static inline int dma_buf_begin_cpu_access(struct dma_buf *dma_buf, + enum dma_data_direction dir) +{ + return -EOPNOTSUPP; +} + +static inline int dma_buf_end_cpu_access(struct dma_buf *dma_buf, + enum dma_data_direction dir) +{ + return -EOPNOTSUPP; +} + +static inline struct sg_table * +dma_buf_map_attachment_unlocked(struct dma_buf_attachment *attach, + enum dma_data_direction direction) +{ + return NULL; +} + +static inline void +dma_buf_unmap_attachment_unlocked(struct dma_buf_attachment *attach, + struct sg_table *sg_table, + enum dma_data_direction direction) { } + +static inline int dma_buf_mmap(struct dma_buf *, struct vm_area_struct *, + unsigned long) +{ + return -EOPNOTSUPP; +} + +static inline int dma_buf_vmap(struct dma_buf *dmabuf, struct iosys_map *map) +{ + return -EOPNOTSUPP; +} + +static inline void dma_buf_vunmap(struct dma_buf *dmabuf, struct iosys_map *map) +{ } + +static inline int dma_buf_vmap_unlocked(struct dma_buf *dmabuf, + struct iosys_map *map) +{ + return -EOPNOTSUPP; +} + +static inline void dma_buf_vunmap_unlocked(struct dma_buf *dmabuf, + struct iosys_map *map) { } + +static inline struct dma_buf *dma_buf_iter_begin(void) +{ + return NULL; +} + +static inline struct dma_buf *dma_buf_iter_next(struct dma_buf *dmbuf) +{ + return NULL; +} +#endif /* CONFIG_DMA_SHARED_BUFFER */ #endif /* __DMA_BUF_H__ */ -- 2.31.1.272.g89b43f80a514

10 months, 3 weeks

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PoC: Memory sharing: vsock + virtio-msg + FF-A + dma-heap

by Viresh Kumar

Hello, I was able to successfully test memory sharing over Vsock, implemented over a virtio message FFA transport. The memory is shared, as an FD, from Linux userspace (via a FFA specific DMA HEAP) and is received in OP-TEE as a buffer, which prints the string written by Linux. Steps to reproduce: - Jens shared an OP-TEE based setup few days back [1]. Reproduce it first. - Migrate to my branches for the following repositories within that: - build, optee_os, optee_test - Path to my repos: git@github.com:vireshk/ - branch: vsock/shmem - Migrate to my linux repo: git://git.kernel.org/pub/scm/linux/kernel/git/vireshk/linux.git virtio/msg - Repeat the same test from Jens's setup: "xtest 2005" - The firmware side will print: Hello from shared memory via FD! This string was written by the Linux userspace in the memory provided by FFA DMA HEAP. Thanks. -- viresh [1] https://linaro.atlassian.net/browse/LEDGE-725

11 months, 3 weeks

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Virtio Message Bus over FF-A 1.0 ALP0 released

by Bertrand Marquis

Hi Everyone, Today, Arm is releasing the first public version of the Virtio Message Bus over FF-A in version 1.0 and in quality state Alpha 0. The document is available for download here: https://developer.arm.com/documentation/den0153/0100 Please contact me if you have any comment, remarks, questions or improvements to suggest so that i can handle them before the spec reaches Beta quality. Regards Bertrand IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.

11 months, 3 weeks

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[PATCH v2 0/4] virtio: Add the virtio-msg transport

by Edgar E. Iglesias

Hi all, This the RFC I'm preparing to send to upstream QEMU for initial RFC review. I didn't see much precedence for Signed-off-by lines in cover letter so instead I'm thinking to explicitely CC Bill and Alex and anyone else who would like to be on copy, just let me know. Changes from v1: * Move VIRTIO_MSG_VENDOR_ID to virtio-msg.c * Update to match recent spec changes (token + set/get_vqueue padding) * Add endian conversion of dev_num and msg_size * Add instructions for running on GPEX PCI x86 microVM and ARM virt * Add missing spsc_queue.h ------------------- This adds virtio-msg, a new virtio transport. Virtio-msg works by exchanging messages over a bus and doesn't rely on trapping and emulating making it a good fit for a number of applications such as AMP, real-time and safety applications. Together with the new transport, this series adds a PCI device that implements an AMP setup much like it would look if two SoC's would use virtio-msg across a PCI link. Current limitations: We only support a single device per bus (dev_num = 0). Shared memory queue layout likely to change in the future. Temporarily uses PCI Vendor Xilinx / Device 0x9039. Missing documentation. The virtio-msg spec: https://github.com/Linaro/virtio-msg-spec/ QEMU with these patches: https://github.com/edgarigl/qemu/tree/edgar/virtio-msg-rfc Linux with virtio-msg suppport: https://github.com/edgarigl/linux/tree/edgari/virtio-msg-6.17 To try it, first build Linux with the following enabled: CONFIG_VIRTIO_MSG=y CONFIG_VIRTIO_MSG_AMP=y CONFIG_VIRTIO_MSG_AMP_PCI=y Boot linux in QEMU with a virtio-msg-amp-pci device, in this example with a virtio-net device attached to it: x86/q35 machine: -device virtio-msg-amp-pci -device virtio-net-device,netdev=n1,bus=/q35-pcihost/pcie.0/virtio-msg-amp-pci/vmsg.0 -netdev user,id=n1 x86/microvm or ARM virt machines: -device virtio-msg-amp-pci -device virtio-net-device,netdev=n1,bus=/gpex-pcihost/pcie.0/virtio-msg-amp-pci/vmsg.0/virtio-msg/virtio-msg-proxy-bus.0 -netdev user,id=n1 Cheers, Edgar Edgar E. Iglesias (4): virtio: Introduce notify_queue virtio: Add virtio_queue_get_rings virtio: Add the virtio-msg transport virtio-msg-bus: amp-pci: Add generic AMP PCI device hw/misc/Kconfig | 7 + hw/misc/meson.build | 1 + hw/misc/virtio-msg-amp-pci.c | 324 ++++++++++++ hw/virtio/Kconfig | 4 + hw/virtio/meson.build | 5 + hw/virtio/virtio-msg-bus.c | 89 ++++ hw/virtio/virtio-msg.c | 598 ++++++++++++++++++++++ hw/virtio/virtio.c | 23 + include/hw/virtio/spsc_queue.h | 213 ++++++++ include/hw/virtio/virtio-bus.h | 1 + include/hw/virtio/virtio-msg-bus.h | 95 ++++ include/hw/virtio/virtio-msg-prot.h | 749 ++++++++++++++++++++++++++++ include/hw/virtio/virtio-msg.h | 45 ++ include/hw/virtio/virtio.h | 2 + 14 files changed, 2156 insertions(+) create mode 100644 hw/misc/virtio-msg-amp-pci.c create mode 100644 hw/virtio/virtio-msg-bus.c create mode 100644 hw/virtio/virtio-msg.c create mode 100644 include/hw/virtio/spsc_queue.h create mode 100644 include/hw/virtio/virtio-msg-bus.h create mode 100644 include/hw/virtio/virtio-msg-prot.h create mode 100644 include/hw/virtio/virtio-msg.h -- 2.43.0

11 months, 3 weeks

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[PATCH v1 0/4] virtio: Add the virtio-msg transport

by Edgar E. Iglesias

Hi all, This the RFC I'm preparing to send to upstream QEMU for initial RFC review. A couple of limitations: I've not updated the protocol with the new msg_token field yet. We only support a single device per bus (dev_num = 0). The kernel driver only works as a module, when building it into the kernel it panics. ------------------- This adds virtio-msg, a new virtio transport. Virtio-msg works by exchanging messages over a bus and doesn't rely on trapping and emulating making it a good fit for a number of applications such as AMP, real-time and safety applications. Together with the new transport, this series adds a PCI device that implements an AMP setup much like it would look if two SoC's would use virtio-msg across a PCI link. The virtio-msg spec: https://github.com/Linaro/virtio-msg-spec/ Linux with virtio-msg: https://github.com/edgarigl/linux/tree/edgari/virtio-msg-6.17 To try it, first build Linux with the following as modules: CONFIG_VIRTIO_MSG=m CONFIG_VIRTIO_MSG_AMP=m CONFIG_VIRTIO_MSG_AMP_PCI=m Boot linux in QEMU with a virtio-msg-amp-pci device, in this example with a virtio-net device attached to it (x86/q35 machine): -device virtio-msg-amp-pci -device virtio-net-device,netdev=n1,bus=/q35-pcihost/pcie.0/virtio-msg-amp-pci/vmsg.0 -netdev user,id=nc Modprobe: modprobe virtio_msg_transport.ko modprobe virtio_msg_amp.ko modprobe virtio_msg_amp_pci.ko You now should see the virtio device. Cheers, Edgar Edgar E. Iglesias (4): virtio: Introduce notify_queue virtio: Add virtio_queue_get_rings virtio: Add the virtio-msg transport virtio-msg-bus: amp-pci: Add generic AMP PCI device hw/misc/Kconfig | 7 + hw/misc/meson.build | 1 + hw/misc/virtio-msg-amp-pci.c | 324 ++++++++++++ hw/virtio/Kconfig | 4 + hw/virtio/meson.build | 5 + hw/virtio/virtio-msg-bus.c | 89 ++++ hw/virtio/virtio-msg.c | 596 ++++++++++++++++++++++ hw/virtio/virtio.c | 23 + include/hw/virtio/virtio-bus.h | 1 + include/hw/virtio/virtio-msg-bus.h | 95 ++++ include/hw/virtio/virtio-msg-prot.h | 747 ++++++++++++++++++++++++++++ include/hw/virtio/virtio-msg.h | 45 ++ include/hw/virtio/virtio.h | 2 + 13 files changed, 1939 insertions(+) create mode 100644 hw/misc/virtio-msg-amp-pci.c create mode 100644 hw/virtio/virtio-msg-bus.c create mode 100644 hw/virtio/virtio-msg.c create mode 100644 include/hw/virtio/virtio-msg-bus.h create mode 100644 include/hw/virtio/virtio-msg-prot.h create mode 100644 include/hw/virtio/virtio-msg.h -- 2.43.0

11 months, 4 weeks

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Notes and updated PR from Oct 23 meeting

by Bill Mills

All, The notes from today's meeting are on the wiki page: https://linaro.atlassian.net/wiki/spaces/HVAC/pages/30311874561/2025-10+Upd… PR #25 has been updated as discussed today and the PR header comment updated with changes. https://github.com/Linaro/virtio-msg-spec/pull/25 Thanks, Bill -- Bill Mills Principal Technical Consultant, Linaro +1-240-643-0836 TZ: US Eastern Work Schedule: Tues/Wed/Thur

11 months, 4 weeks

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Notes and fixed up PR from meeting on 2025/10/16

by Bill Mills

All, The notes from the meeting are here: https://linaro.atlassian.net/wiki/spaces/HVAC/pages/30311874561/2025-10+Upd… PR #25 has been redone to include Bertrand's commits as well as my own. https://github.com/Linaro/virtio-msg-spec/pull/25 I am most interested to know everyones opinion on the removal of the redundant length fields. I am 60/40 against. Thanks, Bill -- Bill Mills Principal Technical Consultant, Linaro +1-240-643-0836 TZ: US Eastern Work Schedule: Tues/Wed/Thur

12 months

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New pull request for RFCv3 spec

by Bertrand Marquis

Hi, I pushed the following pull request to github: https://github.com/Linaro/virtio-msg-spec/pull/24 It is a proposal to handle some things we agreed on modifying in the spec: - header size 8 byte - unique identifier in header - relax error handling to let bus report errors and be coherent with current linux implementation This is a draft and i am definitely open to comments :-) Cheers Bertrand IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.

1 year

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[vmsg][RFC V2 PATCH 0/6] virtio: Add support for Virtio message transport

by Viresh Kumar

Hello, I will try to send this upstream early next week. V2: - Don't limit get/set config to 8 bytes only. - Improved direct/indirect message handling. - Take care of EBUSY error during indirect message. - Static assertions. -------------------------8<------------------------- Hello, This RFC series introduces support for a new Virtio transport type: "virtio-msg", as proposed in [1]. Unlike existing transport types like virtio-mmio or virtio-pci which rely on memory-mapped registers, virtio-msg implements transport operations via structured messages. Those messages can be transported through different mechanisms such as mailboxes, shared memory based FIFO or specific protocols such as FF-A on Arm. This series includes: - Core virtio-msg transport support. - Two message transport bus implementations: - virtio-msg-ffa: based on ARM's Firmware Framework for Arm (FF-A). - virtio-msg-loopback: a loopback device for testing and validation. The code is available here for reference: [3] and virtio-msg loopback test setup is explained here: [2]. This series is based on v6.16-rc6 and depends on commit [4] from linux-next. ### Memory Mapping and Reserved Memory Usage The first two patches enhance the reserved-memory subsystem to support attaching struct device`s that do not originate from DT nodes—essential for virtual or dynamically discovered devices like the FF-A or loopback buses. This reserved-memory region enables: - Restricting all DMA-coherent and streaming DMA memory to a controlled range. - Allowing the remote endpoint to pre-map this memory, reducing runtime overhead. - Preventing unintentional data leaks, since memory is typically shared at page granularity. - For the loopback bus, it restricts the portion of kernel memory that can be mapped into userspace, improving safety. Device association with reserved-memory regions is based on DT node naming conventions, such as vmsglb@ or vmsgffa@, similar to the remoteproc framework’s approach. Feedback on the design, API, and approach is welcome. -- Viresh [1] https://lore.kernel.org/all/20250620224426.3923880-2-bill.mills@linaro.org/ [2] https://linaro.atlassian.net/wiki/spaces/HVAC/pages/30104092673 [3] git://git.kernel.org/pub/scm/linux/kernel/git/vireshk/linux.git virtio/msg-rfc-v1 [4] From linux-next: 5be53630b4f0 virtio-mmio: Remove virtqueue list from mmio device Viresh Kumar (6): of: reserved-memory: Add reserved_mem_device_init() of: reserved-memory: Add of_reserved_mem_lookup_by_name virtio: Add support for virtio-msg transport virtio-msg: Add optional userspace interface for message I/O virtio-msg: Add support for FF-A (Firmware Framework for Arm) bus virtio-msg: Add support for loopback bus MAINTAINERS | 7 + drivers/of/of_reserved_mem.c | 91 ++-- drivers/virtio/Kconfig | 34 ++ drivers/virtio/Makefile | 5 + drivers/virtio/virtio_msg.c | 611 +++++++++++++++++++++++++++ drivers/virtio/virtio_msg.h | 88 ++++ drivers/virtio/virtio_msg_ffa.c | 505 ++++++++++++++++++++++ drivers/virtio/virtio_msg_loopback.c | 323 ++++++++++++++ drivers/virtio/virtio_msg_user.c | 119 ++++++ include/linux/of_reserved_mem.h | 13 + include/uapi/linux/virtio_msg.h | 221 ++++++++++ include/uapi/linux/virtio_msg_ffa.h | 94 +++++ include/uapi/linux/virtio_msg_lb.h | 22 + 13 files changed, 2109 insertions(+), 24 deletions(-) create mode 100644 drivers/virtio/virtio_msg.c create mode 100644 drivers/virtio/virtio_msg.h create mode 100644 drivers/virtio/virtio_msg_ffa.c create mode 100644 drivers/virtio/virtio_msg_loopback.c create mode 100644 drivers/virtio/virtio_msg_user.c create mode 100644 include/uapi/linux/virtio_msg.h create mode 100644 include/uapi/linux/virtio_msg_ffa.h create mode 100644 include/uapi/linux/virtio_msg_lb.h -- 2.31.1.272.g89b43f80a514

1 year

4
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2026

2025

2024

Virtio-msg